I'm not going to comment on array processing techniques, but I suggest you
are into a situation where you have to rethink your database design from
the point of view of performance and normalization.
I don't know how many records you will eventually have, but the key to
performance in SQL databases is the effective use of indexes, and queries
which match. Even if you have an index on the cat_id field, a query like
SELECT * FROM entries WHERE cat_id IN($getcats)
forces the database engine into a sequential read of the cat_id field.
So you can drop the cat_id field from entries and create a new table
entry_cat which has two fields
id
cat_id
Which gives you this query, although I'm a little uncertain about the
bracketing of the condition.
select entries.id, entries.name, entry.cat_id from entries, entry_cat where
(entry_cat.id = 1 || entry_cat.id = 3)
(And which, on reflection, may not yield better performance.)
All this brings me to the question I should have asked up front. How often
will you want to select multiple categories, and will it be done by range
(>2 , <=3) or individual items ( 1 and 5 and 7 )?
I don't think I've been terribly helpful - Miles
At 12:14 PM 7/17/01 +0100, James Holloway wrote:
>Hey guys,
>
>I saw a post in here the other day that's prompted me to ask this
>question... Because I can't seem to get the solution mentioned to work.
>Maybe I'm missing something obvious... Anyway, here goes.
>
>I have a list of categories contained in one table, and a list of entries in
>another. So
>
>categories:
>id name
>1 category1
>2 category2
>3 category3
>
>At the moment, the entries table has a field which contains a field
>mentioning the category by id, so:
>
>entries
>id cat_id name
>1 1 name1
>2 1 name2
>3 1 name3
>
>The problem is this: I'd like to give some entries more than one category.
>I attempted to put the category id's into an array. So a row in the revised
>entries table now looks like this:
>
>entries
>id cat_id name
>1 2 name1
>2 1,3 name2
>3 1 name3
>
>And I'm trying to list from that table with code similar to this:
>
><?
>
>$cat[0] = 1;
>$cat[1] = 3;
>
>$getcats = implode(",", $cat);
>
>$query = @mysql_query("SELECT * FROM entries WHERE cat_id IN($getcats)")
> or die (mysql_error());
>
>// Get the results
>
>?>
>
>I get no errors when executing that code, but I don't get any results back,
>either...... even though I know there are entries in the table with the
>category id listed as 1,3
>
>Any ideas? I'm having "one of those days" :)
>
>Cheers,
>James.
>
>
>
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